1. Field of the Invention
The present invention relates to an enclosure for housing electronic equipment and, more particularly, to a temperature-controlled enclosure for housing remotely located temperature sensitive equipment, such as optical signal processing components for monitoring downhole parameters in oil wells.
2. Description of the Related Art
Electronic equipment produces heat when operated and, when the equipment is located in an environment with extreme ambient temperatures, some means of controlling the temperature of the equipment is typically required. Certain electronic equipment, such as opto-electronic components used in optical signal processing are especially sensitive to temperature variation and require an operating temperature in a relatively narrow range in order to function properly. In the oil production industry, such optical signal processing components, located in a control panel at a wellbore surface, are often used in conjunction with downhole fiber optic sensors to measure various downhole parameters.
Often, such control panels are located in remote locations of the earth and subjected to extreme temperatures, which may subject the components to temperatures in excess of their preferred operating temperature range. It is important the maximum operating temperature is not exceeded in order to prevent damage to the component. Further, some components used in measurement systems, especially those that have very low signal to noise ratios (e.g. capacitive based systems), may suffer degradation in accuracy and resolution due to changing ambient temperatures at the front end of their signal conditioning. Such changes in ambient temperatures naturally occur, for example, between day and night. Therefore, controlling both the stability of the temperature and its magnitude are highly desirable.
Heat generated within the panels may be passively removed, but as the ambient (outside) temperature increases, cooling by passive means becomes less effective. Therefore, in order to compensate for extreme heat, devices such as fans and liquid coolers may be used in order to cool sensitive electronic equipment. However, neither approach is satisfactory if the temperature of the device must be below the outside air temperature. Therefore, in such cases, a device which can produce temperatures below the surrounding air temperature, such as a compressor based refrigerator, is required.
However, cooling systems utilizing refrigerators and fans contain many moving parts and are, therefore, subject to mechanical failure. For example, refrigerating compressor components are subject to mechanical failure and typically require frequent maintenance, However, remotely located control panels are generally required to operate essentially unattended for long periods of time and frequent maintenance is inconvenient and expensive, particularly if production operations are interrupted. Additionally, cooling systems using refrigerators require substantial power to drive the compressor and typically require a reliable external source of electrical power (e.g., line AC service), which is often not available in remote locations.
Accordingly, a need exists for a temperature controlled electrical enclosure that can operate in a remote environment with minimal maintenance, and, preferably, without an external source of reliable electrical power.